Photosensitive composition and method for forming pattern using same

ABSTRACT

The photosensitive composition of the invention contains a polymer material having a group having a structure represented by following general formula (2), and a photo acid generator generating acid with an ultraviolet ray or an ionizing radiation 
                         
wherein m represents an integer of 0 or more.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromthe prior Japanese Patent Application No. 2004-174176, filed on Jun. 11,2004, the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a photosensitive composition and amethod for forming a pattern using the same.

2. Description of the Related Art

A photoresist has been used in the industrial field of electronicdevices requiring various kinds of minute processing, such as asemiconductor integrated circuit including an LSI. As an exposingapparatus used for forming a pattern of the photoresist, a reducedprojection mask aligner, which is generally referred to as a stepper,has been used. Examples of a light source used in the apparatus includethe g line (wavelength: 436 nm), the h line (405 nm) and the i line (365nm) of a mercury lamp, and KrF (248 nm), ArF (193 nm) and F2 (157 nm) asan excimer laser. Exposure with an electron beam and an ion beam alsoattains high resolution processing owing to the short wavelength thereofand can directly form a pattern. Therefore, electron beam lithography isconsidered as being important, and a resist capable of being usedtherefore is demanded.

According to the progress in degree of integration of semiconductorintegrated circuit in recent years, the necessity of the formation offine patterns is being increased, in which the electron beam lithographytechnique, and a resist material and a process technique capable ofbeing used therefore are indispensable.

One of the problems in the electron beam lithography is that thethroughput is inferior to the lithography technique using a stepper.While improvement of the apparatus including the exposure system arenecessary for improving the throughput, improvement of the sensitivityof the photoresist is also an important factor. As simple mathematics,the throughput can be improved twice if the sensitivity is increasedtwice.

The electron beam lithography involves a problem in contamination of anEB column upon EB writing a resist due to a vacuum system included inthe apparatus. This is because of the following reasons. In recentyears, material referred to as a chemical amplification type is used asa photoresist for the electron beam lithography from the standpoint ofsensitivity. The material, in the case of a positive type, has an alkalisoluble group, such as a hydroxyl group, protected with a substituentcapable of being decomposed with an acid. As the substituent in theconventional resist materials, a tert-butoxycarbonyl group, a tert-butylgroup, a trimethylsilyl group, an ethoxyethyl group and the like havebeen used. These protecting groups are released and vaporized intovacuum with an acid generated upon EB writing even in a room temperatureatmosphere in the EB column. The hydrocarbon thus formed deterioratesthe vacuum in the mirror tower to cause failures in the exposure system.

Furthermore, photoresists used in photolithography of the nextgenerations necessarily have a smaller thickness for avoiding a problemin incident distance of incident electrons, a problem in resolution, andparticularly, collapse of patterns. There is such a problem, associatedtherewith, that the etching selectivity is difficult to ensure in thesubsequent processing step of a substrate, and thus a photoresist, whichhas an alicyclic protecting group, improved with etching resistance hasbeen proposed (for example, in J. Photopolym. Sci. & Technol., vol. 16,No. 3, p. 455-458 (2003)).

BRIEF SUMMARY OF THE INVENTION

The photoresist which has the alicyclic protecting group tend to hasproblems in phase separation after coating, increase in edge roughness,and decrease in sensitivity. Furthermore, the photoresist involves sucha problem that it cannot be adapted to various-alkaline-concentrationsdeveloper.

Under the circumstances, an object of the invention is to provide such aphotosensitive composition that can suppress contamination of a mirrortower, has high etching resistance, can solve the problems in edgeroughness, and can be adapted to developer solutions having variousalkali concentrations, and to provide a method for forming a patternusing the photosensitive composition.

According to a first aspect of the invention, a photosensitivecomposition includes: a polymer material having a group having astructure represented by following general formula (1); and a photo acidgenerator generating acid with at least one of an ultraviolet ray and anionizing radiation,

wherein n represents an integer of 1 or more.

According to a second aspect of the invention, a photosensitivecomposition includes: a polymer material having a group having astructure represented by following general formula (2); and a photo acidgenerator generating an acid with at least one of an ultraviolet ray andan ionizing radiation,

wherein m represents an integer of 0 or more.

According to a third aspect of the invention, a photosensitivecomposition includes: a polymer material having a group having astructure represented by following general formula (3); and a photo acidgenerator generating acid with at least one of an ultraviolet ray and anionizing radiation,

wherein n represents an integer of 1 or more, and Z represents one ofgroups represented by the following chemical formula (1)

According to a fourth aspect of the invention, a method for forming apattern, includes: forming a photosensitive layer comprisingphotosensitive composition on a substrate, selectively irradiating thephotosensitive layer with at least one of an ultraviolet ray and anionizing radiation; subjecting the substrate to a heat treatment; anddeveloping the photosensitive layer to remove selectively an irradiatedarea of the photosensitive layer after the heat treatment. Thephotosensitive composition includes: a polymer material having a grouphaving a structure represented by following general formula (2); and aphoto acid generator generating an acid with at least one of anultraviolet ray and an ionizing radiation,

wherein m represents an integer of 0 or more; [0023]

According to the invention, such a photosensitive composition can beprovided that can suppress contamination of an EB column, has highetching resistance, can solve the problems in edge roughness, and can beadapted to developer solutions having various alkali concentrations, andto provide a method for forming a pattern using the photosensitivecomposition.

DETAILED DESCRIPTION OF THE INVENTION

The invention will be described in detail with reference to embodiments.

A photosensitive composition of an embodiment of the invention containsa resin component and an acid generator, and the resin composition is analkali soluble resin having an alkali soluble group, a part or theentire of which is protected with at least one of alicyclic acetalgroups represented by the general formulae (1) to (3).

In the general formula (1), n represents an integer of 1 or more; in thegeneral formula (2) m represents an integer of 0 or more; and in thegeneral formula (3), n represents an integer of 1 or more, and Zrepresents one of groups represented by the following chemical formula(1)

As having been described, a protecting group used in a chemicalamplification photoresist tends to contaminate an EB column. It is wellknown that an acetal group is deprotected with low energy owing to thelow activation energy of chemical reaction, i.e., such protecting grouphaving high sensitivity. For example, an alkyl acetal group representedby a 1-ethoxyethyl group is widely known as a protecting group for aphotoresist, but the alkyl acetal group has such a problem that it iseasily deprotected and vaporized with an acid generated by EB exposure,and contaminates EB column of an EB writing apparatus. Furthermore, theprotecting group itself has no etching resistance, and thus there is aproblem that the photoresist, which have alkyl protecting group, has apoor etching durability.

Even in an alicyclic protecting group, almost same protection ratio(about 20-30%) is needed as alkyl protecting group in order to obtain asolubility contrast between unexposed area and exposed area. In the casewhere the alicyclic protecting group is used for protecting group, aphase separation problem tends to occur after coating, and often causesan increase of line edge roughness since the developer solution does notpenetrate homogeneously. It is supposed that these problems caused bythe great difference in the polarity of alicyclic group and hydroxygroup in the photoresist polymer.

Therefore, the protecting groups that are already disclosed, e.g., thealkyl acetal group and the adamantyl acetal group, are insufficient fora resist material that can be adapted to the next generationlithography.

Under the circumstances, the inventors have made earnest investigationsfor solving the problems, and as a result, it has been found that theproblems can be solved by the embodiment having the aforementionedconstitution.

In the case where the resin component is protected with at least one ofthe alicyclic acetal groups represented by the general formulae (1) to(3), high etching resistance can be obtained, and when the protectinggroup is deprotected with an acid generated by EB exposure, thedeprotected protecting group is difficulty vaporized owing to the largemolecular weight thereof, whereby a EB column can be free from beingcontaminated to some extent. Furthermore, we found that the protectingratio of the hydroxy group in the alkali soluble resin can be reduced incomparison to the conventional protecting groups which are alreadyknown, and thus such a photoresist having high sensitivity can beobtained that is free of such problems as line edge roughness and phaseseparation, and can prevent contamination of an EB column. It isconsidered that this is because the alicyclic part (adamantanederivative) can move flexibly owing to the group (CH₂)_(n) (wherein nrepresents an integer of 1 or more) present between the alicyclic partand the oxygen atom, whereby a large mutual interaction can be obtainedwith the adjacent —OH group to improve the inhibition effect of theprotecting group.

The adamantane derivatives in the general formulae (2) and (3) have alactone structure in the adamantly ring in the molecule thereof, andhave much higher hydrophilicity than the protecting group having nolactone structure. Therefore, the combination of these protecting groupscan control the hydrophilicity of the polymer material (resin), whichgives a great influence on the developing properties. Accordingly, thecomposition can be adapted to developer solutions having various alkaliconcentrations. Furthermore, this adamantyl derivative group (anadamantane ring having a lactonyl group inside), having hydrophilicity,has an intermediate nature (polarity) between the protecting groupsolely having an adamantane structure (strong hydrophobicity) and a —OHgroup in alkali soluble resin (hydrophilicity), whereby penetration ofan alkaline developer into the resin upon developing is carried outhomogeneously, whereby such an effect can be obtained that a line edgeroughness is reduced.

In the positive photosensitive composition of the invention, hydroxylgroups of the alkali soluble resin are preferably protected with atleast one of the groups represented by the general formulae (1) to (3)in an amount of about 4% or more. In the case where the protected amountis about 4% or more, insolubility to an alkali developer solution can beeasily controlled.

The polymer material in the embodiment may have other protecting groupsin addition to the protecting groups represented by the general formulae(1) to (3) Specific examples of the other protecting groups includegroups represented by the following general formulae (4) to (10). Thepolymer material may have one or plural groups selected therefrom.

wherein R represents a hydrogen atom or an alkyl group having from 1 to4 carbon atoms.

In the molecular structures of the groups represented by the generalformulae (1) to (3) in the embodiment, the tertiary carbon atom ofadamantane or the adamantane derivative (an adamantane ring having alactonyl group inside) has the bond toward the alkali soluble group, andthe equivalent effect can also be obtained in the case where thesecondary carbon atom thereof has the bond.

As the alkali soluble resin, to which the protecting group is attached,in the embodiment, a polymer having a phenol derivative, or having analicyclic structure in the polymer backbone, and having a weight averagemolecular weight of from 1,000 to 50,000 is used. Examples thereofinclude a phenol novolak resin, a xylenol novolak resin, a vinylphenolresin, a cresol novolak resin, a copolymer of vinylphenol and an acrylicresin, a norbornene resin having, as a substituent, ethanol substitutedby a trifluoromethyl group, and a copolymer of the norbornene resin andan acrylic resin. The alkali soluble resin preferably has a narrowmolecular weight distribution. Specifically, the alkali soluble resinpreferably has a Mw/Mn (Mw: weight average molecular weight, Mn: numberaverage molecular weight) of 1.2 or less, but the invention is notlimited to the value.

The protecting group can be introduced by an acid catalyst reaction of avinylether compound having the adamantane derivative groups representedby the general formulae (1) to (3) as a raw material and a phenolichydroxyl group. An acid used as the catalyst may be appropriatelyselected from inorganic acids and organic acids. For example,polyhydroxystyrene and vinylether are dissolved in such an amount ofethyl acetate that is 10 times the amount of polyhydroxystyrene, towhich dichloroacetic acid as an acid catalyst is added thereto in anamount, for example, of 5% by weight based on the amount of thepolyhydroxystyrene, and the mixture is stirred at room temperature forabout 12 hours. After neutralizing with an alkali, the reaction mixtureis repeatedly washed with water and then added dropwise to hexane toreprecipitate a polymer in a powder form. In the case where a strongacid is used, there is such a tendency that vinylether is polymerized byitself to fail to obtain the target polymer.

As the acid generator used in the embodiment, compounds that areordinarily used in the photoresist material may be used.

Examples thereof include an onium salt, a sulfonyl compound, a sulfonateester and an organic halide. Examples of the onium salt include adiazonium salt, a sulfonium salt and an iodonium salt, with a counteranion, such as CF₃SO₃ ⁻ and p-CH₃PhSO₃ ⁻, and more particularlypreferred examples thereof include a triallylsulfonium salt and adiallyliodonium salt. The onium salt has been known as an acid generatorhaving good sensitivity to irradiation of an ionic radiation. Specificexamples thereof include a trifluoroacetate salt atrifluoromethanesulfonate salt and a toluenesulfonate salt ofdiphenyliodonium, 4,4′-dibutylphenyliodonium and triphenylsulfonium, andspecifically, diphenyliodonium trifluoromethanesulfonate,di(p-tert-butyl)phenyliodonium trifluoromethanesulfonate,triphenylsulfonium trifluoromethanesulfonate and the like.

The sulfonyl compound is a compound generating sulfonic acid uponirradiation of an ionic radiation, and examples thereof include thosedisclosed in U.S. Pat. No. 5,348,838. Specific examples thereof includephenylsulfonylaectonitrile, bisphenylsulfonylmethane andtriphenylsulfonylmethane.

Examples of the sulfonate ester include nitrobenzyl-p-toluenesulfonate.

The organic halide is a compound forming a hydroacid halide, andexamples thereof include those disclosed in U.S. Pat. Nos. 3,515,552 and3,536,489. Specific examples thereof include2,4,6-trichloromethyltriazine.

The mixing amount of the acid generator is preferably from 0.1 to 20% byweight, and more preferably from 0.2 to 10% by weight, based on thetotal weight of the solid content of the photosensitive composition.

A basic compound may be added to the composition to improve theresolution. Examples of the basic compound include trimethylamine,hexylamine, heptylamine, octylamine, nonylamine, decylamine,stearylamine, aniline, 2-methylaniline, 3-methylaniline,4-methylaniline, 4-nitroaniline, 1- or 2-naphthylamine, ethylenediamine,tetramethylenediamine, hexamethylenediamine,4,4′-diamino-1,2-diphenylethane,4,4′-diamino-3,3′-dimethyldiphenylmethane,4,4′-diamino-3,3′-diethyldiphenylmethane, dibutylamine, dipentylamine,dihexylamine, diheptylamine, dioctylamine, dinonylamine, didecylamine,N-methylaniline, piperidine, diphenylamine, trimethylamine,tripropylamine, tributylamine, tripentylamine, trihexylamine,triheptylamine, trioctylamine, trinonylamine, tridecylamine,triethanolamine, methyldibutylamine, methyldipentylamine,methyldihexylamine, methyldicyclohexylamine, methyldiheptylamine,methyldioctylamine, methyldinonylamine, methyldidecylamine,ethyldibutylamine, ethyldipentylamine, ethyldihexylamine,ethyodiheptylamine, ethyldioctylamine, ethyldinonylamine,ethyldidecylamine, dicyclohexylmethylamine,tris(2-(2-methoxyethoxy)ethyl)amine, triisopropanolamine,N,N-dimethylaniline, 2,6-sopropylaniline, imidazole, 2-phenylimidazole,pyridine, 4-methylpyridine, 4-phenylpyridine, benzylpyridine,3-aminopyrrolidine, 4-methylimidazole, bipyridine, 2,2′-dipyridylamine,di-2-pyridylketone, 1,2-di(2-pyridyl)ethane, 1,2-di(4-pyridyl)ethane,1,3-di(4-pyridyl)propane, 1,2-bis(2-pyridyl)ethylene,1,2-bis(4-pyridyl)ethylene, 1,2-bis(4-pyridyloxy)ethane, guanidine,2-aminopyridine, 3-aminopyridine, 4-aminopyridine,1,1-dimethylguanidine, choline, N-methylpyrrolidone, dimethylimidazole,indoline, piperazine and pyrimidine.

The composition may contain such a tertiary alcohol compound thatfunctions as a water generating agent generating water with the acidcatalyst. Examples thereof include pinacol, cyclohexanol,2,4-dimethyl-2,4-pentanediol, 2,5-dimethyl-2,5-hexanediol,2-ethyl-2-butanol, 3-methyl-1,3-butanediol, 2,3-dimethyl-2-butanol,2-methyl-2-pentanol, 3-methyl-3-pentanol, 2,3-dimethyl-3-pentanol,3-ethyl-3-pentanol, 2-methyl-2,4-pentanediol, 2-methyl-2-hexanol,3-methyl-3-hexanol, 1-methylcyclohexanol, 2-methyl-2-heptanol,2,5-dimethyl-2,5-hexanediol, 2,3-dimethyl-2-hexanol,2,5-dimethyl-2-hexanol, 3,4-dimethyl-3-hexanol, 3,5-dimethyl-3-hexanol,2-phenyl-2-propanol, 3-ethyl-2,2-dimethyl-3-pentanol,2-methyl-1-phenyl-2-propanol, 2-phenyl-2-butanol, 1-adamantanol,menthane-3,8-diol, menthane(6)-2,8-diol, 3,7-dimethyl-3-octanol,2-methyl-2-adamantanol, 3-methyl-2-phenyl-2,3-butanediol,1,1-diphenylethanol, 1,2-diphenyl-2-propanol and benzopinacol.

The ultraviolet ray herein includes the g line (wavelength: 436 nm), theh line (405 nm) and the i line (365 nm), and KrF excimer laser light,ArF excimer laser light and F2 excimer laser light, Extreme Ultravioletlight (EUV) and the ionic radiation herein includes an electron beam, aβ-ray, a γ-ray, an X-ray and neutron radiation.

The photosensitive composition of the embodiment can be produced bydissolving the aforementioned components including the resin componentand the acid generator in an organic solvent. An ordinary organicsolvent can be used for dissolving the photoresit materials. Examplesthereof include cyclohexanone, acetone, methyl ethyl ketone, methylisobutyl ketone, methylcellosolve, methylcellosolve acetate,ethylcellosolve acetate, butylcellosolve acetate, methoxymethylpropionicacid, propylene glycol monomethylether acetate, ethyl lactate, ethylacetate, butyl acetate, isoamyl acetate, γ-butyrolactone,dimethylsulfoxide, dimethylformamide and N-methylpyrrolidone. Theorganic solvent may be used solely or as a mixture of two or more kindsof them.

The method for forming a pattern using the photosensitive composition ofthe embodiment will be described. Varnish of the resist dissolved in anorganic solvent as described above is coated on a substrate by a spincoating method, a dip coating method or the like, and dried at atemperature of 150° C. or less, preferably from 70 to 120° C., to form aresist film. Examples of the substrate include a silicon wafer, asilicon wafer having various insulating layer, electrodes and wiringformed on the surface thereof, a wafer of a III to V Group compoundsemiconductor, such as GaAs and AlGaAs, a quartz substrate havingchromium or chromium oxide vapor-deposited thereon, an aluminumvapor-deposited substrate, a BPSG-coated substrate, a PSG-coatedsubstrate, a BSG-coated substrate, an SOG-coated substrate and a carbonfilm-sputtered substrate.

The resist film is then irradiated with an ultraviolet ray or an ionicradiation through a mask pattern having a shape corresponding to thetarget pattern, or is directly scanning on the surface thereof with anultraviolet ray or an ionic radiation, so as to expose the resist film.

The resist film thus exposed is baked at a temperature of about 170° C.or less by heating on a hot plate or in an oven, by infrared rayirradiation or the like. Thereafter, the resist film is developed by adipping method, a spray method or the like to dissolve and remove theexposed part or the non-exposed part selectively in an alkali solution,whereby the target pattern is formed. Specific examples of the alkalisolution include an organic alkali aqueous solution, such as atetramethylammonium hydroxide aqueous solution and a choline aqueoussolution, an inorganic alkali aqueous solution, such as a potassiumhydroxide aqueous solution and a sodium hydroxide aqueous solution, asolution obtained by adding an alcohol and a surfactant to the aqueoussolutions. The concentration of the alkali solution is preferably 15% byweight or less for obtaining a sufficient difference in dissolution ratebetween the exposed part and the non-exposed part.

The resist pattern thus formed by using the photosensitive compositionof the embodiment has the aforementioned favorable characteristics.

Other steps than those described above may be added to the method of theinvention, and examples of the steps that may be added include a step offorming a flattening layer as an underlayer of the resist film, apretreating step for improving adhesion between the resist film and theunderlayer, a rinsing step of removing the developer solution with waterafter developing the resist film, and a reirradiating step with anultraviolet ray before dry etching.

The invention will be described in more detail below with reference toExamples and Comparative Examples, but the invention is not construed asbeing limited thereto.

EXAMPLE Example 1

100 parts by weight of a resin obtained by protecting 10% of hydroxylgroups of polyhydroxystyrene having a weight average molecular weight of10,000 with a 1-adamantanemethyloxy-ethyl group, 5 parts by weight ofnaphtylimidylcamphor sulfonate as an acid generator, and 20% by mole oftributylamine based on the acid generator were dissolved in methyl3-methoxypropionate as a solvent to prepare a resist solution. Theresist solution was coated on a Si wafer and exposed to an L/S patternby using an electron beam exposing apparatus at an exposure dose of 5μC/cm² (50 KeV) After the exposure, the resist film was baked at 100° C.for 3 minutes and developed with a 0.21 N TMAH aqueous solution for 60seconds. Thus, the exposed part of the resist film was selectivelydissolved and removed to form a positive pattern.

Example 2

100 parts by weight of a resin obtained by protecting 13% of hydroxylgroups of polyhydroxystyrene having a weight average molecular weight of8,000 with a 1-adamantaneoxymethyloxy-ethyl group having a lactone groupintroduced thereto, 5 parts by weight of naphtylimidylcamphor sulfonateas an acid generator, and 20% by mole of tributylamine based on the acidgenerator were dissolved in methyl 3-methoxypropionate as a solvent toprepare a resist solution. The resist solution was coated on a Si waferand exposed by using an electron beam exposing apparatus at anirradiance of 5 μC/cm² (50 KeV) to form the same pattern as inExample 1. After the exposure, the resist film was baked at 100° C. for3 minutes and developed with a 0.13 N TMAH aqueous solution for 60seconds. Thus, the exposed part of the resist film was selectivelydissolved and removed to form a positive pattern.

Example 3

100 parts by weight of a resin obtained by protecting 10% of hydroxylgroups of polyhydroxystyrene having a weight average molecular weight of5,000 with a 1-adamantaneethyloxy-ethyl group, 5 parts by weight ofnaphtylimidylcamphor sulfonate as an acid generator, and 20% by mole oftributylamine based on the acid generator were dissolved in methyl3-methoxypropionate as a solvent to prepare a resist solution. Theresist solution was coated on a Si wafer and exposed by using anelectron beam exposing apparatus at an irradiance of 5.5 μC/cm² (50 KeV)to form the same pattern as in Example 1. After the exposure, the resistfilm was baked at 100° C. for 3 minutes and developed with a 0.15 N TMAHaqueous solution for 60 seconds. Thus, the exposed part of the resistfilm was selectively dissolved and removed to form a positive pattern.

Example 4

100 parts by weight of a resin obtained by protecting 19% of hydroxylgroups of polyhydroxystyrene having a weight average molecular weight of5,000 with a 1-adamantaneoxy-ethyl group having a lactone groupintroduced thereto, 5 parts by weight of naphtylimidylcamphor sulfonateas an acid generator, and 20% by mole of tributylamine based on the acidgenerator were dissolved in methyl 3-methoxypropionate as a solvent toprepare a resist solution. The resist solution was coated on a Si waferand exposed by using an electron beam exposing apparatus at anirradiance of 5 μC/cm² (50 KeV) to form the same pattern as inExample 1. After the exposure, the resist film was baked at 100° C. for3 minutes and developed with a 0.13 N TMAH aqueous solution for 20seconds. Thus, the exposed part of the resist film was selectivelydissolved and removed to form a positive pattern.

Example 5

100 parts by weight of a resin obtained by protecting 11% of hydroxylgroups of polyhydroxystyrene having a weight average molecular weight of5,000 with a 1-adamantaneoxy-ethyl group having a lactone groupintroduced thereto and protecting 6% of hydroxyl groups thereof with a1-adamantaneethyloxy-ethyl group, 5 parts by weight ofnaphtylimidylcamphor sulfonate as an acid generator, and 20% by mole oftributylamine based on the acid generator were dissolved in methyl3-methoxypropionate as a solvent to prepare a resist solution. Theresist solution was coated on a Si wafer and exposed by using anelectron beam exposing apparatus at an irradiance of 5.5 μC/cm² (50 KeV)to form the same pattern as in Example 1. After the exposure, the resistfilm was baked at 100° C. for 3 minutes and developed with a 0.13 N TMAHaqueous solution for 60 seconds. Thus, the exposed part of the resistfilm was selectively dissolved and removed to form a positive pattern.

Example 6

100 parts by weight of a resin obtained by protecting 5% of hydroxylgroups of polyhydroxystyrene having a weight average molecular weight of5,000 with a 1-adamantaneoxy-ethyl group having a lactone groupintroduced thereto and protecting 10% of hydroxyl groups thereof with a1-adamantaneethyloxy-ethyl group, 5 parts by weight ofnaphtylimidylcamphor sulfonate as an acid generator, and 20% by mole oftributylamine based on the acid generator were dissolved in methyl3-methoxypropionate as a solvent to prepare a resist solution. Theresist solution was coated on a Si wafer and exposed by using anelectron beam exposing apparatus at an irradiance of 6.5 μC/cm² (50 KeV)to form the same pattern as in Example 1. After the exposure, the resistfilm was baked at 100° C. for 3 minutes and developed with a 0.16 N TMAHaqueous solution for 60 seconds. Thus, the exposed part of the resistfilm was selectively dissolved and removed to form a positive pattern.

Example 7

100 parts by weight of a resin obtained by protecting 4% of hydroxylgroups of polyhydroxystyrene having a weight average molecular weight of5,000 with a 1-adamantaneoxy-ethyl group having a lactone groupintroduced thereto and protecting 7% of hydroxyl groups thereof with a1-adamantaneethyloxy-ethyl group, 5 parts by weight ofnaphtylimidylcamphor sulfonate as an acid generator, and 20% by mole oftributylamine based on the acid generator were dissolved in methyl3-methoxypropionate as a solvent to prepare a resist solution. Theresist solution was coated on a Si wafer and exposed by using anelectron beam exposing apparatus at an irradiance of 5 μC/cm² (50 KeV)to form the same pattern as in Example 1. After the exposure, the resistfilm was baked at 100° C. for 3 minutes and developed with a 0.13 N TMAHaqueous solution for 20 seconds. Thus, the exposed part of the resistfilm was selectively dissolved and removed to form a positive pattern.

Example 8

100 parts by weight of a resin obtained by protecting 11% of hydroxylgroups of polyhydroxystyrene having a weight average molecular weight of5,000 with a 1-adamantaneoxy-ethyl group having a lactone groupintroduced thereto and protecting 8% of hydroxyl groups thereof with a1-adamantaneethylnxy-ethyl group, 5 parts by weight ofnaphtylimidylcamphor sulfonate as an acid generator, and 20% by mole oftributylamine based on the acid generator were dissolved in methyl3-methoxypropionate as a solvent to prepare a resist solution. Theresist solution was coated on a Si wafer and exposed by using anelectron beam exposing apparatus at an irradiance of 5 μC/cm² (50 KeV)to form the same pattern as in Example 1 After the exposure, the resistfilm was baked at 100° C. for 3 minutes and developed with a 0.16 N TMAHaqueous solution for 60 seconds. Thus, the exposed part of the resistfilm was selectively dissolved and removed to form a positive pattern.

COMPARATIVE EXAMPLE 1

100 parts by weight of a resin obtained by protecting 30% of hydroxylgroups of polyhydroxystyrene having a eight average molecular weight of10,000 with a 1-ethoxy-ethyl group, 5 parts by weight ofnaphtylimidylcamphor sulfonate as an acid generator, and 20% by mole oftributylamine based on the acid generator were dissolved in methyl3-methoxypropionate as a solvent to prepare a resist solution. Theresist solution was coated on a Si wafer and exposed by using anelectron beam exposing apparatus at an irradiance of 5 μC/cm² (50 KeV)to form the same pattern as in Example 1. After the exposure, the resistfilm was baked at 100° C. for 3 minutes and developed with a 0.21 N TMAHaqueous solution for 60 seconds. Thus, the exposed part of the resistfilm was selectively dissolved and removed to form a positive pattern.

COMPARATIVE EXAMPLE 2

100 parts by weight of a resin obtained by protecting 23% of hydroxylgroups of polyhydroxystyrene having a weight average molecular weight of10,000 with a 1-adamantyloxy-ethyl group, 5 parts by weight ofnaphtylimidylcamphor sulfonate as an acid generator, and 20% by mole oftributylamine based on the acid generator were dissolved in methyl3-methoxypropionate as a solvent to prepare a resist solution. Theresist solution was coated on a Si wafer and exposed by using anelectron beam exposing apparatus at an irradiance of 5.5 μC/cm² (50 KeV)to form the same pattern as in Example 1. After the exposure, the resistfilm was baked at 100° C. for 3 minutes and developed with a 0.21 N TMAHaqueous solution for 60 seconds. Thus, the exposed part of the resistfilm was selectively dissolved and removed to form a positive pattern.

Examples 1 to 8 and Comparative Examples 1 and 2 were evaluated forsensitivity, presence of a latent image (evaporation after exposurewithout baking), line edge roughness, resolution and etching resistance.The results obtained are shown in Table 1 below.

TABLE 1 Sensi- Presence of Edge Resolution Etching tivity latent imageroughness (nm) resistance Example 1 good none slight 50 good Example 2good none slight 50 good Example 3 good none slight 50 good Example 4good none slight 50 good Example 5 good none slight 50 good Example 6good none slight 50 good Example 7 good none slight 50 good Example 8good none slight 50 good Comparative good found small 70 poor Example 1Comparative good none large 80 good Example 2

As shown in Table 1, in Examples 1 to 8, the protecting group was notvaporized upon exposure, and good etching resistance was obtained. InExamples 1 and 3, a high inhibition effect of the protecting group wasobserved with the protecting group having high hydrophobicity. Thus, theintroducing amount of the protecting group could be suppressed to 10%,and a resolution of 50 nm L/S could be obtained. The edge roughness wasalso considerably small. In Examples 2 and 4, the introducing amount ofthe protecting group was necessarily larger than Examples 1 and 3 sincea hydrophilic part (lactonyl group) was introduced to the protectinggroup. However, it was observed that the roughness was considerablysmall, and a resolution of 50 nm could be obtained, as similar toExamples 1 and 3.

In Examples 5 to 8, a material having both a hydrophilic protectinggroup and a hydrophobic protecting group was used. As understood fromExamples 5 to 8, the photoresist materials could be adapted to developersolutions having various alkali concentrations by using two kind ofprotecting group. The roughness was considerably small, and a resolutionof 50 nm could be obtained, as similar to Examples 1 to 4.

In the case where an alkyl acetal group was used as in ComparativeExample 1, on the other hand, a patterned latent image was confirmedafter EB exposure without baking, which indicated that the acetal groupwas released and decomposed during EB writing and vaporized into EBcolumn. Furthermore, the protecting group was necessarily introduced inan amount of about 30% due to the low inhibition effect for thedeveloper. Therefore, it was found that larger roughness occurred incomparison to Examples 1 to 8. The resolution was as low as 70 nm. Inaddition, the etching rate was large due to the alkyl group in theprotecting group, whereby the margin of etching selectivity was inferiorto Examples.

In Comparative Example 2, in which a protecting group having a1-adamantane-ethyl group was introduced, no patterned latent image wasfound, which indicated that the protecting group was not vaporized. Theprotecting group having an adamantane group provided a low etching rate,which brought about etching resistance equivalent to Examples 1 to 8.However, the protecting group was necessarily introduced in an amount ofabout 23% in spite of their strong hydrophobicity, whereby deteriorationin pattern shape (large edge roughness) was found, which was likelycaused by inhomogeneous penetration of the developer solution, and theresolution was as low as 80 nm in the EB writing operation under thesame conditions.

1. A method for forming a pattern, comprising: forming a photosensitivelayer comprising a photosensitive composition on a substrate;selectively irradiating the photosensitive layer with at least one of anultraviolet ray and an ionizing radiation; subjecting the substrate toheat treatment; and developing the photosensitive layer to removeselectively an irradiated area of the photosensitive layer after theheat treatment; wherein the photo sensitive composition comprises: afirst polymer material comprising a group having a structure representedby the following general formula (2):

 wherein m represents an integer of 0 or more, a second polymer materialcomprising a group having a structure represented by the followinggeneral formula (3),

 wherein n represents an integer of 1 or more, wherein Z is selectedfrom the group consisting of —O—, —S—, —SO₂—, —O—CH₂, —O—C(O)—O—,—O—C(O)—, and —O—C(O)—CH₂—, and a photo acid generator generating anacid with at least one of an ultraviolet ray and an ionizing radiation.2. The method of claim 1, wherein the photosensitive composition furtherincludes a third polymer material having a group having a structurerepresented by the following general formula (1)

wherein n represents an integer of 1 or more.
 3. The method of claim 1,wherein at least one of the first and second polymer materials comprisean alkali soluble resin having hydroxyl groups.
 4. The method of claim3, wherein the hydroxyl groups of the alkali soluble resin are protectedwith the group represented by the general formula (2) in an amount of 4%or more.
 5. The method of claim 3, wherein the hydroxyl groups of thealkali soluble resin are protected with the group represented by thegeneral formula (3) in an amount of 4% or more.
 6. The method of claim3, wherein the alkali soluble resin has at least one of a phenolskeleton and an alicyclic skeleton.
 7. The method of claim 3, whereinthe alkali soluble resin has a weight average molecular weight of from1,00 to 50,000, and has Mw/Mn of 1.2 or less, wherein Mw represents aweight average molecular weight, and Mn represents a number averagemolecular weight.
 8. A composition comprising a first polymer materialcomprising a group having a structure represented by the followinggeneral formula (2):

 wherein m represents an integer of 0 or more, a second polymer materialcomprising a group having a structure represented by the followinggeneral formula (3),

 wherein n represents an integer of 1 or more, wherein Z is selectedfrom the group consisting of —O—, —S—, —SO₂—, —O—CH₂, —O—C(O)—O—,—O—C(O)—, and —O—C(O)—CH₂—, and a photo acid generator generating anacid with at least one of an ultraviolet ray and an ionizing radiation.9. The composition of claim 8, further comprising a third polymermaterial having a group having a structure represented by the followinggeneral formula (1)

 wherein n represents an integer of 1 or more.
 10. The composition ofclaim 8, wherein an amount of the photo acid generator is 0.1 to 20% byweight based on the total weight of the solid content of thephotosensitive composition.
 11. The composition of claim 9, wherein anamount of the photo acid generator is 0.2 to 10% by weight based on thetotal weight of the solid content of the photosensitive composition. 12.The composition of claim 8, wherein the photo acid generator is at leastone of a compound selected from the group consisting of an onium salt, asulfonyl compound, a sulfonate ester and an organic halide.
 13. Thecomposition of claim 8, wherein at least one of the first and secondpolymer materials comprise an alkali soluble resin having hydroxylgroups.
 14. The composition of 13, wherein the hydroxyl groups of thealkali soluble resin are protected with the group represented by by thegeneral formula (2) in an amount of 4% or more.
 15. The composition ofclaim 13, wherein the hydroxyl groups of the alkali soluble resin areprotected with the group represented by the general formula (3) in anamount of 4% or more.
 16. The composition of claim 13, wherein thealkali soluble resin has at least one of a phenol skeleton and analicyclic skeleton.
 17. The composition of claim 13, wherein the alkalisoluble resin has a weight average molecular weight of from 1,00 to50,000, and has Mw/Mn of 1.2 or less, wherein Mw represents a weightaverage molecular weight, and Mn represents a number average molecularweight.